This paper presents a methodology for the modelling of a 25 kV-50 Hz railway infrastructure, for frequencies from 0 to 5 kHz. It aims to quantify the amplifications of current and voltage harmonics generated by on-board converters into the infrastructure. A circuit is developed to model the skin effect in the overhead line for time-domain simulations. A new approach, based on state space representation and transfer functions, is also proposed to analyse the interactions between trains.

During the design of power converter, design mistakes must be avoided, especially for high voltage and high power converters. Simulation tools can be used to help the designers and limit the risks. This presentation will present a design flow approach used to design and validate a 1.2 kV – 100 kW DC-DC converter which was design from die to converter levels and started for a “blank page”. The presentation is organized in four parts. Firstly, the context of the work is introduced. Then, the simulation flow approach used to validate the design is presented. For this part, the presentation will focus on the system level simulation of one inverter, including the power modules. This part will highlight the main limitations of the current simulation tools found by the designers. In the third part, an enhanced approach is proposed to overcome the limitations and the first results are presented Finally, a conclusion will be presented.

SiC transistors can achieve blocking voltages of 10kV and more. This makes them especially attractive for energy transmission and distribution. Although SiC devices can in theory operate at high temperature (more than 200°C), the on-state resistance of SiC MOSFETs exhibits a strong dependency on the junction temperature. As a consequence, it is shown that these transistors must actually operate at a relatively low junction temperature (less than 100°C) to increase conversion efficiency and prevent thermal runaway. This requirement for high-performance cooling systems has consequences on the packaging technology: the corresponding power modules must both offer a high voltage insulation and a low thermal resistance. In particular, there is a trade-off in the thickness of the ceramic substrate located between the SiC devices and the cooling system. We propose a new substrate structure, with raised features, which improves the voltage strength of a substrate without increasing its thickness. This structure is demonstrated experimentally.

This presentation will provide an update on our current project: designing a cooler for a high power (5 MW) MVDC converter for offshore wind turbines applications. A number of constraints are imposed, mainly related to a limited volume, environmental, safety and health regulations, and of course cooling performance. Indeed, as we presented last year (ATW 2017), the silicon carbide power semiconductors used in this converter should operate at a junction temperature lower than 100 °C for better efficiency.